Battery protection system with reference voltage control system

Abstract

A programmable battery protection system. Implementations may include: a battery and a battery protection integrated circuit (IC) coupled with the battery that includes a reference voltage circuit, a variable resistor circuit coupled with the reference voltage circuit, and only two field effect transistors (FETs) coupled with the overcurrent detection circuit and with the battery. The reference voltage circuit and the variable resistor circuit may be configured to cause a current sense signal of the system to vary substantially linearly with changes in a supply voltage of the system.

What is claimed is: 
     
       1. A programmable battery protection system comprising:
 a battery; and 
 a battery protection integrated circuit (IC) coupled with the battery comprising:
 a reference voltage circuit; 
 a variable resistor circuit coupled with the reference voltage circuit; and 
 an overcurrent detection circuit coupled with the reference voltage circuit; and 
 only two field effect transistors (FETs) coupled with the overcurrent detection circuit and with the battery; 
 
 wherein the reference voltage circuit and variable resistor circuit are configured to cause a current sense signal of the system to vary substantially linearly with changes in a supply voltage of the system. 
 
     
     
       2. The system of  claim 1 , wherein the reference voltage circuit and variable resistor circuit are configured to cause an overcurrent signal of the system to be substantially invariant to changes in a supply voltage of the system. 
     
     
       3. The system of  claim 1 , wherein the reference voltage circuit comprises a supply voltage detector circuit, a bandgap buffer circuit, and an amplifier operatively coupled together. 
     
     
       4. The system of  claim 1 , wherein the variable resistor circuit comprises an array of fuses coupled with one or more sets of a plurality of switching components coupled in parallel with one or more sets of a plurality of resistors wherein the states of the array of fuses are configured to open or close corresponding switching components of the one or more sets of the plurality of switching components, permitting one or more summed resistances generated by the one or more sets of the plurality of resistors to be changed. 
     
     
       5. The system of  claim 1 , wherein the overcurrent detector circuit is configured to use a reference voltage generated by the reference voltage circuit to evaluate whether one of a discharge overcurrent condition and charging overcurrent condition exist and to, in response to detecting the one of the discharge overcurrent condition and the charging overcurrent condition, disconnect the only two FETs from the battery. 
     
     
       6. The system of  claim 1 , wherein the only two FETs and the battery protection IC are comprised in the same semiconductor package. 
     
     
       7. The system of  claim 4 , wherein the states of the array of fuses are configured to be set using a trimming signal generated during an initial testing of the on resistance of the only two FETs. 
     
     
       8. The system of  claim 4 , wherein the array of fuses comprise polyfuses. 
     
     
       9. The system of  claim 4 , wherein the states of the array of fuses are configured to be set using a laser trimming signal based on a specified on resistance of the only two FETs. 
     
     
       10. The system of  claim 4 , wherein the overcurrent detector circuit is configured to use a reference voltage generated by the reference voltage circuit and the one or more summed resistances to evaluate whether one of a discharge overcurrent condition and a charging overcurrent condition exist and to, in response to detecting the one of the discharge overcurrent condition and the charging overcurrent condition, disconnect the only two FETs from the battery. 
     
     
       11. The system of  claim 1 , wherein the battery protection IC further comprises a temperature variation correction circuit comprising a diffused resistor coupled to a constant current source and the amplifier, wherein the diffused resistor is configured to change the reference voltage output from the amplifier as a resistance of the diffused resistor changes as a function of the temperature of the diffused resistor. 
     
     
       12. The system of  claim 11 , wherein the temperature variation correction circuit is configured to cause the current sense signal of the system to vary substantially linearly with changes in temperature of the diffused resistor. 
     
     
       13. A battery protection integrated circuit (IC) for a battery protection system, the circuit comprising:
 a reference voltage circuit comprising a supply voltage detector circuit, a bandgap buffer circuit, and an amplifier, the reference voltage circuit configured to supply a reference voltage that is a function of a supply voltage; 
 a variable resistor circuit coupled with the reference voltage circuit, the variable resistor circuit comprising an array of fuses coupled with one or more sets of a plurality of switching components coupled in parallel with one or more sets of a plurality of resistors wherein the states of the array of fuses are configured to open or close corresponding switching components of the one or more sets of the plurality of switching components, permitting one or more summed resistances generated by the one or more sets of the plurality of resistors to be changed; and 
 an overcurrent detection circuit coupled with the reference voltage circuit; 
 wherein the overcurrent detector circuit is configured to use the reference voltage generated by the reference voltage circuit and the one or more summed resistances to evaluate whether one of a discharge overcurrent condition and charging overcurrent condition exist and to, in response to detecting the one of the discharge overcurrent condition and the charging overcurrent condition, disconnect a battery from one of a load and a charger. 
 
     
     
       14. The IC of  claim 13 , further comprising a temperature variation correction circuit comprising a diffused resistor coupled to a constant current source and the amplifier, wherein the diffused resistor is configured to change the reference voltage output from the amplifier as a resistance of the diffused resistor changes as a function of the temperature of the diffused resistor. 
     
     
       15. A method of providing a reference voltage to an overcurrent detection circuit of a battery protection integrated circuit (IC), the method comprising:
 substantially linearizing a response of a current sense signal of a battery to changes in a supply voltage of the battery by:
 using a plurality of states stored in an array of fuses, setting a summed resistance of a plurality of resistors coupled to a plurality of switching components coupled with the array of fuses; 
 using the summed resistance and a supply voltage detector comparator, generating a current by converting variation in the supply voltage into a current; and 
 using the current and a bandgap buffer circuit and an amplifier, generating a reference voltage for use by an overcurrent detector circuit. 
 
 
     
     
       16. The method of  claim 15 , wherein the current increases when the supply voltage decreases and the current decreases when the supply voltage increases. 
     
     
       17. The method of  claim 15 , further comprising using the overcurrent detector circuit and the reference voltage to evaluate whether one of a discharge overcurrent condition and a charging overcurrent condition exist and to, in response to detecting the one of the discharge overcurrent condition and the charging overcurrent condition, disconnect the battery from one of a load and a charger. 
     
     
       18. The method of  claim 15 , using a temperature variation correction circuit to substantially linearize the response of the current sense signal of the battery to changes in temperature. 
     
     
       19. The method of  claim 18 , wherein the temperature variation correction circuit comprises a diffused resistor coupled to a constant current source and the amplifier, and wherein the method further comprises changing the reference voltage output from the amplifier as a resistance of the diffused resistor changes where the resistance of the diffused resistor is a function of the temperature of the diffused resistor. 
     
     
       20. The method of  claim 19 , wherein the reference voltage rises as the temperature rises as a function of the impedance of the diffused resistor.